This invention relates to a semi-conductor assembly of the kind including, as active components, a thyristor and a diode, the diode having its anode connected to the cathode of the thyristor and its cathode connected to the anode of the thyristor.
One practical application of a semi-conductor assembly of the kind specified is in a forced commutation circuit, for example, a thyristor chopper circuit for controlling operation of an electric motor driving an electrically propelled vehicle. In such an application the active components of the semi-conductor assembly must be capable of dealing with very high currents (for example in excess of 150 amps) and a problem exists in producing a suitable assembly at reasonable cost. For example, in one suitable known form of semi-conductor assembly of the kind specified the thyristor and diode are integrated in a single semi-conductor chip, the diode being in annular form encircling the thyristor. It is found however that the manufacture of such an integrated device results in a high percentage of faulty components and thus manufacturing costs are high. An alternative approach is to use discrete thyristor and diode packages, but in view of the relatively massive nature of the package, which is necessary in order to provide the required high current rating, it is found that the electrical connections between the discrete diode and thyristor packages have an undesirably large inductance.